The present invention relates to a medical instrument and, in particular it concerns a cervical dilation monitor.
By way of introduction, it is still standard practice for the obstetrician to resort to regular vaginal examination in order to estimate cervical dilation and thereby assess the progress of labor during the first stage of active labor. The cervix dilates to about 10 cm during this stage of labor as well as effacing to a very thin layer. However, these examinations are uncomfortable to the patient, inaccurate, objective, as well as risking introducing infection into the uterus, these disadvantages being amplified if serial examinations are carried out by different observers.
Of relevance to the present invention is U.S. Pat. No. 5,658,295 to Krementsov which teaches an instrument, similar to calipers, with a scale for indicating dilation. The device taught by Krementsov is not designed to be left in position for continual monitoring. Additionally, the instrument is not disposable and requires repeated sterilization.
Of most relevance to the present invention is U.S. Pat. No. 4,141,345 to Allen et al. which teaches an expandable V-shaped caliper instrument. The dilation is measured using strain gauges. A shortcoming of the aforementioned system is that the system is not disposable and requires repeated sterilization.
Also of relevance to the present invention is U.S. Pat. Nos. 4,476,871 to Hon and 6,423,000 to Berry. Both of these patents teach systems for monitoring cervical dilation. However, both of the systems are non-disposable, expensive as well as intrusive to the patient.
There is therefore a need for a cheap, disposable cervical dilation monitor which is easy to fit and is comfortable and safe for the patient, takes into account cervical effacement, as well as providing accurate, continuous and objective measurements of cervical dilation.